Bazooka Localizes to Dendritic Branch Points in the Drosophila

The development and positioning of dendrites is an important field in neuroscience, and while we have learned a great deal about dendritic branching from motor and sensory neurons of the peripheral nervous system, the molecular activities controlling dendrite placement in the central nervous system are much less understood. Recently, a three dimensional map of the Drosophila third instar central brain has been published, subdividing bundles of neurons originating from the same neuroblast into specific lineages. The axonal and dendritic projections from each lineage appear to be invariant among different individuals, presenting the unique opportunity to study the molecular basis for dendrite placement in the larval central brain. In previous studies, members of the Par-complex have been found to localize to dendritic compartments in both cultured rodent hippocampal cells as well as motor neurons of the Drosophila embryo. What role the Par-complex plays in the dendritic compartment and how the Par-complex localizes to that area remains unknown. To address these questions, we use the UAS/GAL4 system to determine if members of the Par-complex localize to points of dendritic branching in the recently categorized neuronal lineages of the third instar brain. Using a UASBazooka:GFP conjugation, we drive Bazooka:GFP with lineage specific GAL4 lines and find that Bazooka localizes to the proximal dendritic branch point in secondary axon tracts. To verify that Bazooka is required for the branching process, we use MARCM analysis of mutant Bazooka lineage clones and assay for missing proximal branches. Lastly, because dendritic branch points of the larval and pupal brain appear in close proximity to the axonal/glial point of contact, we also study the role of glia interaction with the proximal branch point and its possible role in Bazooka localization. To what extent other members of the Par-complex localize to and affect dendritic branching, and if this is common to all lineages of the central brain, are intriguing future points of study.